Brake mechanism



March l5, 1960 1 GOLDMAN 2,928,506

BRAKE MECHANISM Filed March 22, 1957 fam/mm 29 Y /I wy ATTORNEYS BRAKE MECHANISM Leo Goldman, Detroit, Mich., assigner to Rockwell- Standard Corporation, a corporation of Pennsylvania Application March 22, 1957, Serial No. 647,774

7 Claims. (Cl. 18S-78) This invention'relates to vehicle brake mechanism and particularly to return spring attachment arrangements for internally expanding brakes.

In its pcrferred embodiment the invention will be described as specifically applied to a brake assembly wherein dual web pivoted brake shoes are oppositely urged to brake retracted position by a return spring interconnecting the respective shoe webs. Prior to the invention it was conventional to interconnect a corresponding opposed web of such dual web shoes by a single spring such as disclosed in Super Patent No. 2,568,777, issued September 25, 1951. However difficulties in assembly and operation were encountered due to the unbalance of spring forces and the resultant tendency of the shoes to tilt laterally with respect to their support. This resulted in uneven wear at the pivot anchor pins for the brake shoes,`and increased the need for frequent adjustment besides reducing the overall lining life.

The present invention corrects this ditliculty by providing a return spring and dual web brake shoe association wherein the spring forces tending to oppositely pivot the shoes exert essentially no lateral tilting .forces on the shoes. This is done by providing a special lcentered bridge between the webs on the respective shoes for opposite end attachment to the return spring.

it is the major object of the invention to provide a novel dual web pivoted shoe brake assembly wherein the shoe webs have balanced connection with a single return spring in such manner that the spring has essentially no tendency to tilt the shoes laterally of their pivot axes.

A further object of the invention is to provide a novel brake assembly wherein a special return spring connecting member is mounted to bridge the dual webs of each brake shoe.

it is a further object of the invention to provide in a dual web brake shoe a centered bridge member formed `for attachment of one end of a return spring and mounted between the webs so that it is readily installed or intentionally removed but is not accidentally detached from operative position.

A further object of the invention is to provide a novel integral return spring attachment member for mounting between the webs of a dual web brake shoe.

Further objects of the invention will appear as the description proceeds in connection with the appended claims and the annexed drawings wherein:

Figure 1 is a side elevation showing the general brake assembly embodying the invention and showing the return spring connection;

.Figure 2 is a fragmentary view mainly in Vsection on nite States Patent" line 2 2 of Figure 1 and showing the return spring at' tachrnent member in operative position bridging the dual shoe webs;

Figure 3 is an enlarged side elevation of the bridge member showing details of structure;

Figure 4 is an end elevation of the bridge member of Figure 3; and

Figure 5 is a section on line 5-5 of Figure 3. t

In the illustrated embodiment of the invention dual web brake shoe assemblies 11 are pivoted at adjacent ends on parallel axis anchor pins at 12 carried by a rigid suitable backing plate or other support. The opposite ends ofthe shoe assemblies rotatably carry cam follower rollers 13 urged into engagement with a rotatable actuating cam 14 by a single return spring 15 as will appear. The shoes 11 are essentially the same although oppositely pivoted so that spring 15 normally urges them toward brake retracted position.

Each shoe assembly 11 comprises an arcuate platform 16 upon which is cemented or riveted one or more blocks 1'/ of friction liner material, and spaced parallel at coextensive webs 18 and 19 are rigid with the concave side of platform 16. Platform 16 and webs 18 and 19 are preferably fabricated from sheet metal sections suitably formed and Welded together, and webs 18 and 19 are parallel to the side edges of platform 16 and equally spaced therefrom.

At the pivot ends each shoe web 18 and 19 is formed with similar anchor pin mounting apertures 21 in coaxial alignment. At the opposite ends each shoe web18 and 19 is formed with similar open end journals 22 in coaxial alignment, and these journals rotatably support the oppositely projecting shaft sections 23 of cam follower rollers 13.

Near the cam follower end of each shoe assembly the web s lvand 19 are formed with coaxial circular apertures 24 and 25ct the same size, and a bridge member 26 is mounted with opposite ends disposed in these apertures.

Bridge member 26 is integrally formed from a length of round wire stock and comprises similar end sections 27 and 28 in axial alignment',v and an odset intermediate sec` tion 29. Preferably member 26 is formed from a suitable length of Mt" diameter round spring steel wire that will retain a given shape. As will appear bridge member 26 is rigid enough not to'appreciably deflect yduring normal operation of the brake assembly but it is suiliciently longitudinally flexible to slightly deform and spring back to shape during insertion and removal.v Intermediate section 29is connected to the end sections by inclined portions 31 and 32, and as shown in Figure 4 the entire bridge member is symmetrical about a plane containing the axes of the end and intermediate sections. Y

At the juncture of the inclined portions of the bridge with the associated end sections relatively thin tlat ribs 33 ,and 3d are provided, these being preferably formed by acompressive action of the metal wire at those places to squeeze the metal outward into ilat lrib shape extending substantially radially of the wire and in the opposite direction diametrically from the offset intermediate section 29.

At the opposite ends of the bridge member are formed inclined surfaces 35 and 36, these being inclined about 30 tothe common axis of the end sections and divei'ging i* in the direction of theoffset section 29V. Surfaces 35 and 36 lie in planes that intersect at 9D?. Y The intermediate section 29 is formed with a central lateral groove or depression 37 which is preferably formed by bending the'wire at that point. 'In practice the wire is sinuously bent in the intermediate section so that depression 37 is ankedlby raised formations 38 and 39. The adjacent end of spring-15 is formed intoV a hook at 41 as shown in Figure V1 to fit over into depression 37 between Y the raised formations 38 and 39 that keepV the hook from being laterally displacedoward either web in the acteristics thereof.

fAs `shown in Figure 4 theintermediate section-29 is displaced'into'fsubstantially parallel lateral offsetrrelation-4 to `theend sections by a distancev approximately' equal to the diameter of the wire.` As shown in Figure?, the Ybridge member `26 has a maximum transverse -dimen-r sionwA measured' between parallel planes containing the outer tips of33 and 34 and the opposite side of the intermediate section 29, and this dimension A is greater than the diameter B of apertures 24 and 25 so thatthe position of Figure 3V after uncoupling spring 15, a punch may be employed to drive one end axially throughits associated aperture, and then it can be removed by hand. In this action the bridge member resiliently exes temporarily when driven by the punch. It will be seen that the bridge member 26 may be assembled with its shoe for inventory and shipping and there will be no danger of Thel inventionmay. beV embodied in other speciic its accidentally dropping out. l f

' forms without departing from the spirit or essential char- The present embodiment is therefore to` be considered in all respectsV as illustrative and not restrictive, the scope of the invention being indicated by the. appended claimsrather than by the foregoing description, and all changes. which come within the meaning and range of equivalency` of the claims are therefore intended to be embraced therein. j

What is claimed and desired to be secured by United States LettersPatent is: Y

1. An internally expanding j brake comprising two t Vbrake shoe assembliesvpivoted at adjacent ends and opbridge `member cannot pass straight through the `dualVV webs.

member 26` is heat treated to relieve strains induced by forming. The beveledV ends V35 and 36 AVmerely facilitate entryof the end sections into the web apertures.

v The bridgemembei 26 may be inserted by hand either end tirst from either side `of the webs, land Figure 3 shows in dottedlines insertion fromrthe rightpinto vthe limittpos'ition towhich it may usually be pushedjmanual ly.V It will be noted that at this point the inclined cam' or wedge surface 42has encountered the edge-tof aperture Y2,4, and the opposite end section 28 has entered aperture 25.A Then axial force is applied-r to member 26,

as by tapping it with a hammer, and the inherent springiness of the bridge member resiliently flexes it temporarily and enables surface 42 to cam past aperture 25;

` The same action takes place when inclined cam or wedge surface 43 of'rib 33 encounters the edge of,V aperture 25,

After being` formed to the shape of Figure` 3 the bridge eratively connectedto an actuator at their other ends, each of said shoeY assemblies having an axiallyspaced l pair of side Aby side longitudinal `webs substantially centrally disposed of the shoe assembly and the webs of each'shoe assembly beingV formed with aligned apertures, a return spring-attachmentV member bridging each pair of I webs and having' its `opposite ends freely mounted in said apertures and YanV intermediate` section offset laterally from saidfends; .inthe space between said webs, and a` returri'spring connected at* opposite ends substantially centrally of said intermediate sectionsof said members, said return Vspring being under tension in the assembly and -normally tending to rock said shoe assemblies to-` ward-each other, and each said attachment member having -a `transverse dimension measured between parallel j planes containingthe opposite-outer sides o f said `offset and Vthus, eventually the bridgeV member` 2 6 Vis driven like a `nail `into thejwebs so that the end sections 2'l7ran'd 28 are disposed in the apertures 24 and 25 respe't i\ lely,V

and the intermediate section 29 is disposed inthe space between the webs 18 and 19. The cylindrical'surfaces of -end sections 27 and 28 will be effectively journalled on the circular bearing edge areas of apertures 24" and 25, andrwith thef bridge members 26 inserted into both brake shoes the return spring may now be attached. This is done `by pivotally hooking the hook 41 over the.

depressions 37 in the bridge members 26 of the opposedy Since the spring 15 is-.thus under-tension the shoes. bridgeL members 26 willbepulled to the sides of .the web aperturesV opposite the platform 16, Vas shown inFigure l. This is-facilitatedby the rocking sliding bearing enf' section' and said ends greater than the maximum transverse dimensionof at least one of its associated web apertures, and each said `member being suiciently flexiblerand resilient to deect during insertion or removal with ,respect tosaid web apertures and spring backto f original condition.

internally jexpanding `brake comprising two `brake shoe assemblies pivoted at adjacent ends and op- Veratively connected to anjactuator at their other ends,

each of said shoe assemblies` having a pair of side by side. axially spaced longitudinal kvwebs vsubstantially centrallyJV disposed of the shoe,.asscmbly andA the webs of each pairybeing-v formed,- with apertures `that provide e aligned arcuate bearing surfaces, a return spring attach-o gagement `of the end sections ofthe bridge members in therweb apertures,{and as shown in Figure 2 it locates each bridge member 26 in such position in the brake assembly that the ofset'section Y29 is offset` with respect to the web apertures and cannot beV laterallyVv displaced to Vany appreciable extent.

.The bridge member 26 isisymmetrical andhasV these u mentrnemberbridging Yeach pair of webs having opother; Y 3. An Vintegral `return spring'attachment bridge for a A ldual web `brake shoe comprising axially spaced and cam or wedge surfaces 42,1" 43 located for insertioniu j either direction as shown.V In practicerthe surfaces 42,`

43 are usually 1A" radius surfaces on "the ribs.

Since` the depressions 37 are located centrally of the bridge members and therefore centrally of the ,brake shoes in the assembly the force exerted by spring `15` tending to oppositely rock Vthe shoes r11 about anchor pins 12 is effectively exerted in a plane about perpendicular f t`o the axes of'anchor pins 12 and "thereforethere is little or no tendencyofV the brake shoes 11 to tilt due to springV tension. The bridge members-26V automatically j Ycenter the return spring between the brake shoes 11.

j .'IctV remove the^ bridgermemberz.frornthe vfull line' aligned ysimilarA end sections, an intermediate section' Vlaterally offset Vto said end sections: means defining inclined cam surfaces on said end sections adjacent their juncturewith 'saidofset intermediatesection and projectt ing from said endsections in they` opposite direction from said offset section, and a spring attachment station located substantially Ycentrally of said intermediate section.

4. In the{ return spring attachment bridge defined in claim 3, said return spring attachment station being a surface depression .in said intermediate section.

5 An integral return spring attachment bridge member made from a single length of round Awire stock comprising similar coaxial end sections;a'substantiallyrparallel` intermediate section laterally oiset from said end sections and having oppositely inclined portions connecting opposite ends of the intermediate section with the end sections longitudinally aligned ribs formed on said end sections to project in the direction opposite from said oiset section, and a spring end mounting formation substantially centrally of said intermediate section.

6. In the bridge member dened in claim 5, said forma tion being a surface depression in said intermediate section anked by relatively raised regions.

7. The bridge member defined in claim 5, said mernber being symmetrical about a plane containing said ribs and the axes of the end and intermediate sections,

, s and being symmetrical on both sides of'said spring end mounting formation.

References Cited in the le of this patent UNITED STATES PATENTS 2,568,777 Super Sept. 25, 1951 2,601,006 Rodabaugh June 17, 1952 2,710,076 Russell June 7, 1955 FOREIGN PATENTS 22,766 Great Britain Oct. 6, 1909 542,112 Great Britain Dec. 24, 1941 

